What you do in the job?
A feature film, or commercials director will hire a Casting Director to assist them the casting of many of the roles in the film.
The director will probably have a clear idea of his/her leads, but will often leave a lot of the decisions with a casting director.
The task of casting is involves great knowledge of talent and getting hold of people from various agents.
As their assistant you will be drawing up contracts, liaising with agents and artists, and setting up casting sessions. You will sort video equipment to record the casting sessions in order to show the talent to the director later. There will be plenty of routine office work.
What qualities are required?
By the very nature of the job, a Casting Director will need a great knowledge of the people available. So a great deal of experience and time in the industry is necessary.
Great communication skills, both on the phone and face to face. Good negotiating skills and the ability to bluff! Stamina and the ability to work long and unsociable hours (at 'social' events, to meet talent) An ability to read people well.
To break in you will need a degree, good office skills - IT and phone etc as mentioned, and the patience to learn on-the-job.
No specific degree, but a degree will of course help. Experience of working in any of the service industries is good experience, and you'll clearly have the skills to interview very well.
How you start and where you can go with it?
Start as assistant - then move around to perhaps bigger/different casting directors, then take the bold step and go for it on your own and you may well want to start your own business.